<div class="problemindexholder" problemindex="C">
 <div class="ttypography">
  <div class="problem-statement">
   <div class="header">
    <div class="title">
     C. From Y to Y
    </div>
    <div class="time-limit">
     <div class="property-title">
      time limit per test
     </div>
     1 second
    </div>
    <div class="memory-limit">
     <div class="property-title">
      memory limit per test
     </div>
     256 megabytes
    </div>
    <div class="input-file">
     <div class="property-title">
      input
     </div>
     standard input
    </div>
    <div class="output-file">
     <div class="property-title">
      output
     </div>
     standard output
    </div>
   </div>
   <div>
    <p>
     <span class="tex-font-style-it">
      From beginning till end, this message has been waiting to be conveyed.
     </span>
    </p>
    <p>
     For a given unordered multiset of
     <span class="tex-span">
      <i>
       n
      </i>
     </span>
     lowercase English letters ("multi" means that a letter may appear more than once), we treat all letters as strings of length
     <span class="tex-span">
      1
     </span>
     , and repeat the following operation
     <span class="tex-span">
      <i>
       n
      </i>
      - 1
     </span>
     times:
    </p>
    <ul>
     <li>
      Remove any two elements
      <span class="tex-span">
       <i>
        s
       </i>
      </span>
      and
      <span class="tex-span">
       <i>
        t
       </i>
      </span>
      from the set, and add their concatenation
      <span class="tex-span">
       <i>
        s
       </i>
       +
       <i>
        t
       </i>
      </span>
      to the set.
     </li>
    </ul>
    <p>
     The cost of such operation is defined to be
     <img align="middle" class="tex-formula" src="/predownloaded/a5/7f/a57f90e0efabfb23990aab1eb18fb8c18477cea7.png" style="max-width: 100.0%;max-height: 100.0%;"/>
     , where
     <span class="tex-span">
      <i>
       f
      </i>
      (
      <i>
       s
      </i>
      ,
      <i>
       c
      </i>
      )
     </span>
     denotes the number of times character
     <span class="tex-span">
      <i>
       c
      </i>
     </span>
     appears in string
     <span class="tex-span">
      <i>
       s
      </i>
     </span>
     .
    </p>
    <p>
     Given a non-negative integer
     <span class="tex-span">
      <i>
       k
      </i>
     </span>
     , construct any valid non-empty set of no more than
     <span class="tex-span">
      100 000
     </span>
     letters, such that the minimum accumulative cost of the whole process is
     <span class="tex-font-style-bf">
      exactly
     </span>
     <span class="tex-span">
      <i>
       k
      </i>
     </span>
     . It can be shown that a solution always exists.
    </p>
   </div>
   <div class="input-specification">
    <div class="section-title">
     Input
    </div>
    <p>
     The first and only line of input contains a non-negative integer
     <span class="tex-span">
      <i>
       k
      </i>
     </span>
     (
     <span class="tex-span">
      0 ≤
      <i>
       k
      </i>
      ≤ 100 000
     </span>
     ) — the required minimum cost.
    </p>
   </div>
   <div class="output-specification">
    <div class="section-title">
     Output
    </div>
    <p>
     Output a non-empty string of no more than
     <span class="tex-span">
      100 000
     </span>
     lowercase English letters — any multiset satisfying the requirements, concatenated to be a string.
    </p>
    <p>
     Note that the printed string doesn't need to be the final concatenated string. It only needs to represent an unordered multiset of letters.
    </p>
   </div>
   <div class="sample-tests">
    <div class="section-title">
     Examples
    </div>
    <div class="sample-test">
     <div class="input">
      <div class="title">
       Input
      </div>
      <pre>12<br/></pre>
     </div>
     <div class="output">
      <div class="title">
       Output
      </div>
      <pre>abababab<br/></pre>
     </div>
     <div class="input">
      <div class="title">
       Input
      </div>
      <pre>3<br/></pre>
     </div>
     <div class="output">
      <div class="title">
       Output
      </div>
      <pre>codeforces<br/></pre>
     </div>
    </div>
   </div>
   <div class="note">
    <div class="section-title">
     Note
    </div>
    <p>
     For the multiset {
     <span class="tex-font-style-tt">
      'a'
     </span>
     ,
     <span class="tex-font-style-tt">
      'b'
     </span>
     ,
     <span class="tex-font-style-tt">
      'a'
     </span>
     ,
     <span class="tex-font-style-tt">
      'b'
     </span>
     ,
     <span class="tex-font-style-tt">
      'a'
     </span>
     ,
     <span class="tex-font-style-tt">
      'b'
     </span>
     ,
     <span class="tex-font-style-tt">
      'a'
     </span>
     ,
     <span class="tex-font-style-tt">
      'b'
     </span>
     }, one of the ways to complete the process is as follows:
    </p>
    <ul>
     <li>
      {
      <span class="tex-font-style-tt">
       "ab"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      }, with a cost of
      <span class="tex-span">
       0
      </span>
      ;
     </li>
     <li>
      {
      <span class="tex-font-style-tt">
       "aba"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      }, with a cost of
      <span class="tex-span">
       1
      </span>
      ;
     </li>
     <li>
      {
      <span class="tex-font-style-tt">
       "abab"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      }, with a cost of
      <span class="tex-span">
       1
      </span>
      ;
     </li>
     <li>
      {
      <span class="tex-font-style-tt">
       "abab"
      </span>
      ,
      <span class="tex-font-style-tt">
       "ab"
      </span>
      ,
      <span class="tex-font-style-tt">
       "a"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      }, with a cost of
      <span class="tex-span">
       0
      </span>
      ;
     </li>
     <li>
      {
      <span class="tex-font-style-tt">
       "abab"
      </span>
      ,
      <span class="tex-font-style-tt">
       "aba"
      </span>
      ,
      <span class="tex-font-style-tt">
       "b"
      </span>
      }, with a cost of
      <span class="tex-span">
       1
      </span>
      ;
     </li>
     <li>
      {
      <span class="tex-font-style-tt">
       "abab"
      </span>
      ,
      <span class="tex-font-style-tt">
       "abab"
      </span>
      }, with a cost of
      <span class="tex-span">
       1
      </span>
      ;
     </li>
     <li>
      {
      <span class="tex-font-style-tt">
       "abababab"
      </span>
      }, with a cost of
      <span class="tex-span">
       8
      </span>
      .
     </li>
    </ul>
    <p>
     The total cost is
     <span class="tex-span">
      12
     </span>
     , and it can be proved to be the minimum cost of the process.
    </p>
   </div>
  </div>
  <p>
  </p>
 </div>
</div>
